Hydraulic circuit



' Aug. 21, 1945. G. A. wfxHLlvlxRlKI 2,383,092

' HYDRAULIG CIRCUIT Filed Sept. l5, 1941 2 Sheets-Sheet l Aug. 21, 1945. G. A. WAHLMARK 2,383,092

HYDRAULIC CIRCUIT Filed Sept. l5, 1941 2 Sheets-Sheet 2 www www www ww www ww www aiented Aug.. L. i945 2,383,092 HYDRALIC CIRCUIT Gunnar A.` Wahlmark, Rockford, Ill., assignor to Sandstrand Machine Tool Co., Rockford, Ill., a corporationI of Illinois Application September 15, 1941, Serial No. l110,860

18 Claims.

The invention relates to a hydraulic circuit, including a hydraulic transmission composed of a pump and a motor, and relates more particularly to such a circuit especially adapted for use with machine tools.

One object of the invention is to provide a hydraulic circuit of new and improved construction resulting in venhanced operation.

Another object is to provide in a circuit having a variable displacement pump and a motor means operable automatically with an increase in the working pressure of the pump t increase slightly the pump displacement to compensate for increased leakage at such increased Working pressures.

Another object is to provide in a circuit having a variable displacement pump with a control member governing the displacement of the pump means operable to maintain aconstant pressure on the control member regardless of variation in the working pressure of the pump.

Another object is to provide in a circuit, having a main pump and a motor with a closed circuit, a make-up and control fluid pump, and means responsive to the working pressure of the main pump operable with an increase in pressure to increase the pressure of the make-up pump, permitting low make-up pump pressure at idling and normal working pressures of the main pump.

Another object is to provide in a circuit having a variable and reversible displacement pump with a control member governing the volume of displacement and hydraulic means operable independently to govern the direction of displacement and conjointly with the control member to govern the volume of displacement, means for parent from the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatic view ofracircuit embodying the features of my invention.

Fig. la is an enlarged detail View taken along the line |a-la of Fig. 1.

Fig. 1b is an enlarged detail View taken along the line lb-Ib of Fig. 1.

Fig. 2 is a fragmentary view taken along the line 2-2 of Fig. 1.

Fig. 3 is an enlarged view of the reversing valve means only of the 'directional control valve means showing the same in one feed position.

Fig. 4 is a similar view of the reversing valve means but showing the same in the opposite feed position.

modifications and alternative constructions, it is supplying control uid, and means responsive to y the working pressure of the pump to increase the pressure of the control fluid supplied to the hydraulic means with an increase of the working pressure.

Still another object is to provide in a circuit,

.including a pump and motor. hydraulically actuated means for governing the direction of operation of the motor and pilot valve means of new and improved construction controllingr the supply of operating uid to the hydraulically actuated direction governing means.

Still another object of the invention is to provide a direction governing valve means including a hydraulically shiftable valve member having a neutral position and a position on either side of neutral, and plunger valves normally maintain-r ing no pressure on the shiftable valve member.

Other objects and advantages will become ap- `here shown in the drawings and will hereinafter be described in a preferred embodiment. However, it is not intended that the invention is to be limited thereby tothe specific embodiment disclosed. On the contrary, it is intended to cover all modifications and alternative constructions falling within the spirit and scope of the invention as defined in the appended claims.

The circuit comprises generally a hydraulic motor, generally designated M, a mainv pump, generally designated P, for supplying operating fluid to the motor, and an auxiliary pump, generally designated.- MP, for supplying make-up and control fluid. The pump and the motor are connected in a closed hydraulic circuit which 1s provided with suitable relief valves to prevent excessive high pressures and with check valves to prevent the working pressure from backing up against the make-up pump. The main circuit additionally includes a valve means for controlling the pressure of the fluid discharged by the make-up4pump, valve mea-ns for providing a supply of make-up and control fluid under constant pressure, valve means for controlling the direction of operation of the motor, and valve means for determining the rate of operation of the motor, particularly the feed rate of operation. Preferably the pump and motor are arranged in an end to end relationship and may be enclosed in a single housing to formt-a unitary l'rlfnsmsion such as that disclosed m my copending application Serial No. 414,587, led October 11, 1941. Among other things, the housing provides a reservoir or tank T for the fluid employed in the circuit.

The pump P is of the wobbler type and basi-` cally is identical in construction with the pump disclosed in my copending application Serial No.

410,861, filed of even date herewith. The pump P comprises a cylinder block 9 having one end, herein its outer or right hand end, non-rotatably received within a casing member I0. At the end of the cylinder block opposite the casing member I0, in fact interposed between the pump and the motor, is a common valve block I I. The faces of the valve block `II are formed with circular recesses I2 and I3, of which the recess I2 with the end of the cylinder block 9 forms a valve chamber housing valve means, more particularly described ,hereinaften The cylinder block 9 is formed with a plurality of parallel, longitudinally extending and annularly arranged cylinders I4 opening at their left ends. as viewed in Fig. 1, to the valve chamber I 2 through an annular series of ports l5, and at the other ends opening without restriction to the in- 1 terior of the casing member Ill. Reciprocable in each cylinder I4 is a piston I6 adapted in all posi-- block is a stepped bore having a first portion IB 4a recess 25 in the block I Il and with its outer end projecting outwardly of the casing member I for connection with a motor, is a shaft 26. Near its inner end the shaft is journaled in a roller bearing 21 seated inthe portion 2I of the stepped.y

`bore, while near its outer end the shaft is surrounded by a sleeve 28 formed with a radially projecting flange 29. The casing member Il) is provided with an inwardly extending annular 'flange through which the shaft 26 projects. Mounted in the casing member I6 adjacent the ange I0 is an annular ring 30, generally L-shaped in cross section, and between the ring and the sleeve 28 there is interposed a roller bearing 3l, while between the ring and the flange 29 there is interposed a roller bearing 32, respectively supporting the shaft radially and against end thrust.

The actuating means I1 here takes -the form of a wobbler composed of an inner annular member 35, pivotally mounted on the shaft 26 by means of a pin 36, and an outer annular ringl member 31. This ring member 31 is rotatable relative to the inner member 35, and to that end is generally T- shaped in cross section, and interposed between the members 35 and 31 is a ball bearing 38, to take the radial thrust, and a roller bearing 39, to take the end thrust. The member 31 is, of

course, disposed to engage the projecting ends ofv surface of the member 31 is such that the moment arms of that half of the wobbler on one side I0' providing a circular opening I0" 50 oi the pin 36 (in Fig. 1, upper half) will have such proportion with respect to the moment arms of that half of the wobbler on the other side of the pin 36 (in Fig. l, lower) as to tend to cause the reaction of the pistons on the wobbler to restore the same to neutral or no-stroke position.

In order to control the flow of fluid into or out of the cylinders I4, there is interposed in the chamber I2 a wheel-like or spoked valve 42, such as more particularly disclosed and claimed in my Patent No. 2,190,812, dated February 20, 1940. -This valve is mounted eccentrically with respect 'to the shaft 26 and to that end such eccentric mounting is here obtained by the employment of l5 an eccentric cam 43 non-rotatably secured on the end of the shaft 26 by means such as a pin 44. The outer rim or periphery 45 of the valve 42 serves, due to the eccentric movement of the valve, to connect the ports I5 alternately to the outer circumferential portion of the chamber I2, or to an annular passage 46 formed by the spokes 41 of the valve. This annular passage in the Valve is always in communication with an annular passage 48 formed in the block Il which opens to the chamber I3 in a manner similar to its opening to the chamber I2. The outer portions of the chambers I2 and I3 are interconnected by a passage 49 to complete a hydraulic circuit between the pump and the motor.

Unique governing means of a character more particularly disclosed and claimed in my copending application Serial No. 410,861, filed of even date herewith, are herein provided for determining the position of the wobbler. Comprising this governing means-is a cylindrical control member or cam 5I slidable longitudinally in the portion I9 of the stepped bore in the cylinder block 9, so as to be concentric of the shaft 26 and also concentric of the wobbler I1. At its right hand end, as viewed in Fig. l, the'control cam 5I is enlarged ,to form a 'piston 52 slidable in the portion I8 of the stepped bore. At its extreme right hand end 'the control cam 5I is provided with an end edge disposed in a plane at right angles to the shaft 4"', 26 and adapted to bear against the inner member 31 of the wobbler to determine the angular position of the wobbler. The piston portion 52 of the control cam 5I, in cooperation with the shoul., der 20, forms a hydraulic means which, as presently -will .become more apparent, is utilized to place the wobbler under a pre-load of a predeter- Vmined constant pressure. The angular position of the wobbler I1 is determined .by longitudinal shift of the control cam 5I. Shift to the right is, 55 of course', limited and determined by contact of the cam with the wobbler 31 throughout its entire circumference, thewobbler in this position being disposed strictly at right-angles to the shaft in an absolute zero or no-stroke position. Shift of the control cam to the left, as viewed in Fig. 1, is limited by abutment of the end of the cam with the shoulder 22. -Intermediate positions of the cam c are determined by means later described.

Shift of the wobbler fromone side to the other of its neutral position to obtain reversal of operation of the pump, `tharis reversal in the direction of fluid discharge, is obtained by means op.- erating independently of the control cam 5I. Herein this means is hydraulic and comprises an annular piston 55 xedly secured on the shaft 26 by means such as a pin 56. Cooperating with the piston is a cylinder 51 having a narrow extension 58 slidable in a groove 59 formed in the periphery of the shaft for that purpose. Extending radially fromthe extension 59 is an arm 60 received in a suitable socket 6I formed in the inner member 35 of the wobbler.

Passages for the supply of operating fluidto opposite ends of the cylinder 51 are formed in part in the shaft 26. Extending longitudinally of the shaft is a passage 65 connected by a radial passage 66 to the left hand end of the cylinder 51 at a point immediately adjacent the piston 55. A similar radial passage 61 opens to the right hand end of the cylinder 51 immediately adjacent the piston 55 and communicates at its inner end with a longitudinal passage 64. At its left hand end, the passage 65 is connected by a radial passage 68 to an annular groove 69 formed internally of a sleeve or bushing 10 in the reduced portion 23 of the stepped bore. Spaced from the groove 69 is a similar groove 1| connected by a radial passage 12 to the passage 64, The grooves 69 and 1| are supplied with control iiuid, as hereinafter more particularly described.

The motor M is also of the wobbler type and is generally similar to the pump P. Like the pump, it is comprised in the main of a cylinder block I having formed therein a plurality of annularly arranged and longitudinally extending cylinders 16, each of which opens at its inner or right hand end, as viewed in Fig. 1, through a port I1 to the recess I3. Reciprocable in each of the cylinders is a piston 18, at all times pro- Vof the cylinder block 15 cooperates with the recess I3 to form a valve chamber, while the outer .or left hand end of the cylinder block is non` rotatably received Within a casing member 19.

Formed in the cylinder block 15 is a longitudinally extending bore 8|, and extending longitudinally of the motor centrally of the bore 0| isl a shaft 82 projecting at its left end, as viewed in Fig. 1, outwardly of the casing member 19. The shaft 82 is journaled atl its inner end and intermediate its ends in ball bearings 83 and 84, respectively. Near its outer end, it is journaled in a pair of roller bearings 85 and 86 the same as the pump shaft. Surrounding the shaft and closing the opening in the casing member 19,

through which the end of the shaft projects, is

a conventional seal 90.

Pivotally mounted on the shaft 32 on a pin 93 is a wobbler, generally designated 94, identical with the Wobbler I1 of the pump. The angular position of the wobbler with respect to the'shaft 82, and hence the displacement of the motor, is governed by a bar 95 slidable longitudinally of the shaft-in a groove 96. Intermediate its ends, the bar is provided with an arm 91 terminating in a rounded head received in a socket 99 approximately formed in the Wobbler 94. At its inner end the bar 95 is engaged with the inner race |00 of ball bearings IOI, the outer race of which is formed by an extension |02 of an annular member |03 slidable and rotatable relative to the shaft 82. The member |03 is shifted longitudinally of the shaft to vary the displacement only of the motor by means presently to be described.

The low of fluid from the pump to the motor is controlled by a wheel-like valve |04 identical with the valve 42 This valve operates in the valve chamber |3 and isldriven in timed relation with the reciprocation ofthe pistons by the shaft 82. As best seen in Fig. 1b, there projects eccentrically from the end of the shaft and into the Chamber I3 a stud |06. This Studis received in a ball bearing I 01 interposed between the stud and the valve.

Individual means are provided for determining intermediate positions of the control cam 5| of the pump and for shifting the annular member |03 of the motor. Herein the means for shifting the control cam of the pump includes a crank |08 pivoted on a pin |09 journaled in an upstanding housing I I0 secured to the casing member I0. The crank has an arm I|| projecting through registering apertures ||2 and ||3 formed in the casing member I0 and the cylinder block 9,; respectively, into engagement with a slot I I4 formed in the control cam 5I. A forked arm ||5 of the crank extends at right angles to the arm III to cooperate with a shoulder ||6 formed on each of a pair of pisto'ns ||1 and II 9 (see Figs. 1 and 2). The pistons ||1 and ||8 are reciprocable, respectively, in cylinders ||1 and II8 formed in part in the housing ||0 and in part in the casing member I0. Opening to the lower end of the cylinder I I1 is a port ||1, and opening to the lower end of the cylinder IIB' is a port IIB". Threaded through the housing |I0 in position to be abutted by the pistons ||1 and IIB are a pair of limit screws ||9 adjustable to determine the extent of upward movement of the pistons ||1 and IIB under the influence of control fiuid supplied to the lower ends of the cylinders. As best seen in Fig. 1, the screws ||9 determine the position of the shoulders I I6 and thus the extent of rotation in a clockwise direction of the crank |08. Such limitation of the clockwise rotation of the crank |08 in turn limits the shift of the control cam 5I to the left, and thus determines the positions of the control cam intermediate the extreme positions previously mentioned. This means is employed, as will presently become more apparent, to determine the position of the control cam when it is desired to obtain a feed rate of operation of the motor M,

and it is to that end that the various parts are nally thereof, in which is reciprocable a double- \-.|3| formed in the annular member |03.

ended piston |22. The cylinder is closed at its ends by caps |23 and |24 threaded thereinto, with the cap |24 having threaded therein and Vadapted to extend therethrough an adjusting screw |25 protected by a screw ca p |26. The cylinder has opening to one end thereof a port |21, and openingto the other end thereof a port |28. Intermediate its ends thepiston I 22 is provided with a recess |29 into which projects one end of a lever |30, the other end of which projects into a socket The lever is pivoted intermediate its ends and for that purpose is formed with a ball-like enlargement |32 received in a socket |33 formed in a bushing received in the cylinder block 15. The lever |30 is secured to the piston |22 by means of a pin |34, and, of course, the cylinder |20 and the casing member 19 are provided with registering apertures |35 and |36, respectively, to permit move'- ment of the lever |30 under the iniiuence of the piston' 22. As fluid is supplied to one end or the other of the cylinder |20, the piston is `shifted either to the position shown, or to the left, intoY When in abutment abutment with the cap |23. with the cap |23, however, the wobbler has not been reversed but has merely been returned to an approximate perpendicular or no-stroke position.

Control fluid for the various hydraulic 'devices heretofore described and make-up fluid for the closed pump-motor circuit is supplied by the make-up pump MP previously mentioned. This make-up pump is of the rotary gear element typeelement |4 and a crescent shaped dividing melnber |42. 'Ihe elements operate in a chamber formed by the outer end face of the casing member and an end closure |43 secured by bolts |44 to the casing member |0. Fluid is drawn into the pump through an intake passage, generally designated |45, and composed of a bore 45' in the casing member |0 and a conduit |45". The passage communicates atone end with .the tank T and terminates at the other end in an enlarged recess- |46 forming the intake port for the makeup pump. A strainer |41 preferably is interposed in' the intake passage. A similar enlarged recess |48 forms the dischargeport for the makeup pump, and leading from this recess is a makeup and control fluid supply passage |49 terminating in a threaded port |50.

Incorporated in the circuit to perform various functions, primarily the governing of the fluid supplied by the make-up pump, are a plurality of valve means including a pair of high pressure relief valve means, generally designated and |52, a pair of check valves, generally designated |53 and |54, a control fluid pressure governing valve means, generally designated |55, and a pressure reducing valve means, generally designated |56. These valve means are all described, particularly as to physical structure, in my copending application Serial No. 410,861, led of even date herewith. Suffice it to say, therefore, that each of the high pressure valve means vcomprises a bore |51 opening to the end of which, through an annular seat |58, is a port |59, and opening |15, will be described in greater particularity hereinafter.

The pressure reducing valve comprises a bore |82 in which is reciprocable a cylindrical valve |83. The valve is formed intermediate its ends withan annular groove |84, and extending longitudinally of the valve are a plurality of passages |85 opening at one end to the groove |84 and at the other end opening through the end of the valve. 'Ihe valve isA urged by a compression spring |86"to abut a boss |81. Opening to the annular chamber formed about the boss |81 is a port |88, and opening to the side of the bore'r |82 is a port |89 controlled by the valve |83. The port |89 is so located that it registers with the groove |84 when the valve abuts the boss |81, and is gradually closed as the valve is shifted away from the boss against theaction of the spring |86. The valves justv described can all conveniently be located directly in the transmission proper, usually the Valve block i in much the same manner more fullydisclosed in my copending application Serial No. 410,861, filed of even date herewith.

Forming a feature of this invention, and therefore not disclosed in the related cases, is a directional control valve means, generally designated 90. This means comprises a valve bore |9| in which is reciprocable a valve |92 of the cylinder type. Opening to one end of the bore is a port |93, and opening to the other end of the bore is a port |94, while intermediate those ports the bore is formed with five annular grooves |95, |96, |91, |98 and |99, suitably spaced to permit cooperation with the valve |92, a's will later become more apparent. The valve |92 is formed with a passage 200 extending longitudinally thereof, but not opening through the ends thereof,

' and communicating with a wide annular recess to the side of which is a port |60. Cooperating with the .seat |58 is a disk valve 6| urged to seated position by a strong compression spring |62. Each of the check valve means comprises a bore |63 openingV to the end of which, through an annular valve seat |64, is a port |65, and opening to the other end of which is a port |66. A disk valve |61 is urged to seating position by a light compression spring |68.

The control pressure governing valve means |55 is formed with three bores |69, |10 and |1|, successively decreasing in diameter. Reciprocable in the first bore is a piston valve |12 urged-toward engagement with a boss |13 by alight compression spring I14. Reciprocable in the bore |10 is'a plunger |15 having a reduced portion |16 raciprocable in the bore |1|. The area of the end of the reduced portion |16 and of the annular shoulder formed on the plunger |15 surrounding the reduced portion |16 are equal; Opening to theannular chamber formed about the boss |13,

so as to be constantly open, is a port |11, `and opening to theopposite end of the bore |69, and

also always open, is a port |18. Opening to the I the purpose of the equal areas on the plunger 20| formed externally of the valve at one end thereof and with three narrower annular recesses 202, 203 and 204. Also formed in the valve, in one-half thereof, is a longitudinal passage 205 communicating with external annular recesses 206 and 201, while formed in the other half of the valveis a passage .208 communicating with annular recesses 209 and 2 I0. These longitudinal passages, likewise, do not open through the ends of the valve, but do open to a recess 2|| formed centrally of the valve. The recess 2|| is provided to receive the end of an arm 2|2 of manually or dog operable means for shifting the valve which is not here disclosed, but which is disclosed in my application Serial No. 350,475, filed August 3, 1940. Incidentallythe casing housing the valve means |90 is formed with a chamber 2 |3 to accommodate the arm 2|2, which-chamber is connected to the tank. In the position slwn in Fig. 1, the Valve 92 occupies a neutral position and may be shifted either to the right or to the left to occupy a feed or a traverse position on either side of neutral. Positions nearest neutral are feed positions, and 'positions on one side of neutral represent forward operation of the motor, jwhile positions on the other side of neutral represent reverse operaton of the motor. The valve is yieldably held in its positions by a conventional means, such as a spring pressed detent 2|3' engaging notches 2 3".

The valve |92 is also intendedto be shifted hydraulically from one extreme position through neutral to the other extreme position. Such shift 1s here under the control of, a pair of plunger valve means, generally designated 2|4 and 2|6. These valve means are identical and each comaasaooa prises a valve bore |`2|8 opening at its inner end y to a chamber or recess 2|1. Reciprocable in the bore is a valve 2|8 projecting through the outer end of the bore 2|6 so as to be capable of actuation by means such as a dog, and formed on' its inner end with a flange 2 9 disposed in the cham-l ber 2|1 and serving to limit the outward movement of the valve which is constantly being urged outwardly by a compression spring 220. The valve is provided with awide annular recess 22| formed externally thereof and a narrow annular f recess 222 disposed outwardly of the recess 22|. Disposed -beyond the recess 222 is a leakage :duid trapping groovev223 which communicates through radial ports with a longitudinal passage 224 extending through the inner end of the valve. The valve bore2|6 is formed with an annular groove 225 and ports 226, 221 and 228. Each valve/has two positions, namely, that shown in Fig. 1, and that shown in Fig. 5. In the position shown in Fig. 1, the recess 222 registers with groove 225, recess 22| registers with ports 226 and 221, and port 228 is closed. In the position shown in Fig. 5, recess 222 bridges groove 225 and pori-l 226, while port 221 is now bridged with port 228 by the rei cess 22|. The grooves i225 of the valve means are interconnected by a passage 229, the ports 226 are connected by a passage 230, and the ports 228 are connected by a passage 23|, which is bya passage 232 connected to the chamber 2 |1, which in turn is by a passage 233 connected to the chamber 2|3 y designated 234, which governs, as will presently become apparent, the supply of control uid to the Acylinders ||1 and ||8f. 'Ihis valve means cornprises a valve bore 235 in which is reciprocable a valve 236 projecting outwardly of the bore at one end for actuation by suitable means, such4 as a dog. `The valve is urged/ outwardly of the' bore cby a compression spring 231 and is formed with a wide annular recess 238 and narrower annular recesses 239 and 240 on opposite sides of the recess 238. Both the recesses 239 and 240 are connected by radial ports with an axial bore 24| opening through one end of the valve to the bore 235.

The valve bore 235 in turn is formed with a port 242 flanked on either side by a groove 243 and a groove 244.A The valve has two positions, namely, that shown in Fig. 1,y wherein the recess 238 bridges the groove 243 and the port 242 with the recess 240 of. the valve registering with the groove 244, and a position shifted axially inwardly of that shown in Fig. 1, wherein the recess 238bridges port 242|and groove 244, while recess 239 registerswith grooves 243.

*The` manner in which the various valve means, as well as the hydraulic devices, are connected in circuit will now be described. Leading from the port |58 is a make-up and control uid conduit 250. This supply conduit-is connected direct to the port |11 of the pressure governing valve meansl |55 and, by\a branch conduit 25|, is connected to the port 225 of the directional control valve means to supply control huid at the pressure maintained by the valve lmeans |55. A branch conduit 252 is connected yto the port |89 250 to maintain a constant pressure in the annular chamber about the boss |81. By way of example, the pressure herein maintained is in the order of 100 pounds per square inch. This constant pressure furnishes the make-up iluid for the closed pump-motor circuit and also furnishes fluid at constant pressure for the control cam 5|. To'that end, a conduit 253 leads from the pont |88 direct to the annular space formed between the shoulder 20 and the piston portiony 52 `of the control cam 5|. Branching from the .conduit 253' is a conduit 254 dividing into con- -duits 255, 256, respectively, leading to the pas- `valves |53 and |54.

sages 48 and 49 formed in the valve block I, and having respectively interposed therein .the check These check valves are arranged in well known manner to permit flow from the conduit 254 to the passages 48 and 49, but preventing flow in .the reverse direction. The high pressure relief valves |5| and |52 are connected to the conduits 255 and 256 to relieve fluid from the discharge or working side of the closed circuit and .to return it to the return side should the working pressure become excessive. Morevparticularly, a conduit 251 leads from the conduit 255 to the port |59 of the valve means |5|, while the port |60 of this valve means is by a conduit 258 connected to the conduit 256. In V like manner the port |59 of the valve means |52 is connected to the conduit 256 by a conduit 259, while the port |60 is connected to the conduit 255 by the conduit 260.

Aiding the spring |14 of the valve means |55 to maintain lthe supply conduit 250 at at least .the pressure desired to be maintained by the v pressure reducing valve means |56, a branch conduit 26| leads from .the conduit 253 to the port |18 of the control fluid pressure governing valve means |55. In order to maintain pressures varying with :the working pressures of the main pump Jregardless of the direction in which the main pump is discharging, the ports |80 and |8| are,

respectively. connected by conduits 262 and 263 to the conduits 256 and 255, thus subjecting the ,equal areas formed on the plunger |15 to the men-ting those described is a passage or a conduit 265 leading from the groove 225 of the valve means 2|4 to the groove |95 of the valve means |90 and leading from the ports 221 of the valve means 2|4 and 2|5 are conduits 266v and 261,

' respectively, connected .to the ports |93 and |94.

7of the pressure reducing valve means |56. The y valve means |56 operates in well known manner The grooves |91 and |98 are by conduits 268 and 269 connected, respectively, to the annular grooves 69 and 1| formed in the sleeve 23 surrounding the pump shaft 26 so as to supply control fluid to opposite sides of thecylinder 51. Groove |99 is by a conduitx210 connected to the pont |28 of the motor displacement governing device, while groove |96 is by a conduit 21|\connected to the port |21 of Ithat device.

A conduit 212 branches from the conduit 21| to supply control iluid to the feed valve means 234 and to that end is connected to the port 242. The annular grooves 243 and 244 of this valve means are by conduits 213 and 2 14 connected, respectively, to the ports HI8" and ||1 of lthe feed control cylinders ||8' and ||1. Fluid returned from the cylinders ||1' and H8' and leakage fluid are discharged to the tank through means including a conduit 215.

For a better understanding of the invention, the operation will now be described. Let it be assumed that the shaft 26 of the pump P is being driven and that the valve means are in the positions shown, more particularly, that the valve |92 is in its neutral position and that the valve 236 is in its outer position.

Under those circumstances, .the make-up pump MP will be discharging make-up and control fluid to lthe conduit 250, which will then now through the conduit 25|, groove 225 of valve means 2|5, connecting passage 229, groove 225 of valve means 2|4, and conduit 265 to groove |95 of the valve means |90. Though control fluid thus is supplied -to .the longitudinal passage 200, neither end of the cylinder 51 is under pressure since the grooves |91 and |98 are now connected to the tank. With-no pressure acting in either end of the cylinder 51, but with the reaction of the piston |6 of the main pump P on the wcbbler |1 tending to restore the same to its nostroke position, coupled with the action of the fluid on thecontrol cam .the wobbler I1 will be returned to its absolute neutral or no-stroke position. With no fluid discharged by the main pump P, the pressure governing valve means |55 maintains only the minimum pressure for which it is adjusted, namely, approximately 110 pounds per square inch, which is sumcient to supply make-up and also to pre-load the wobbler through the hydraulic means formed in part by the control cam 5|. Thus, though the pump is being driven, no fluid is being supplied to the motor M. It will be apparent that under `these conditions the make-up pump need supply fluid only at the low pressure required for make-up and for placing the wobbler under a constant pre-load, which pressurel as previously stated, is in the order of 100 pounds per square inch.

If now the operator is ready to initiate operation of the motor, it is only necessary that the valve |92 be shifted. The initial `shift will, of course, be through the manual means and may be either to one of the feed positions or to one of the traverse positions. Let it be assumed that it is desired to drive the motor at a feed rate and that the valve |92 has been shifted to the ri-ght as shown in Fig. 3. Under those circumstances control fluid will still be supplied through the conduit 265 to the longitudinal bore 200 of the valve. -In this-position of the valve,

recess 202 opens to both grooves |96 and |91.A

Thus control fluid is supplied through the conduit 268 to the left hand end of the cylinder 51, ,thereby through the extension 58 urging the wobbler |1 away from its absolute zero displacement position perpendicular to the shaft 26. Fluid from the right hand end of the cylinder 51 is discharged through radial passage 61, passage 64, radial passage 12, groove 1|, and conduit 269 to groove |98, recess 209, and longitudinal passage 208 to the tank.v At the same time control fluid issupplied through the conduit 21| to the left hand end of the cylinder |20, the right hand end of the cylinder |20 being through conduit 210 connected to groove |99 which is now also open to tank through the recess 2|0 and longitudinal passage 208. 'I'he piston |22'in the cylinder 20 will thus be shifted to the right to the position shown in Fig. 1 and will, through the lever |30, shift the member |03 to the left,

tilting the wobbler 94 to the maximum stroke 1date herewith. Though the pressure of the con-l position which, of course, is the slow speed or feed rate position ofthe motor wobbler. With the supply of control fluid to the conduit 21|,

there is also a supply of control fluid through the 5 conduit 212 to the port 242 of the feed valve means 234. In the position shown, this valve means 234 conducts the control fluid from port 242 to groove 243 and thence through 'conduit 2.13 4to the cylinder -|,|8, shifting the piston ||8 upwardlyA until it abuts its adjustable limit screw H9, all as shown in Fig. 1. The piston ||8 in turn determines the -position of the crank |08 and as here adjusted permits only-slight shift of the control member 5| to the left. The pump will thus have but a small displacement which, coupled with the large displacement of the motor, will result in operation of the motor at a slow feed rate.

It is believed clearly understood from the foregoing description that the cylinder 51 and the piston 55 are of such dimensions that the force generated by the action thereon of the control fluid at the pressure maintained by the valve means |55 is at all times sufficient to overcome the reaction of the pistons on the wobbler and the force of the control member 5|, so that the wobbler is at all times held against the end edge of the control member 5|.

In order that the pressure of the wobbler on the edge of the control member 5| may remain constant regardless of the variation of the working pressure in the pump, due to the variations in load on the motor, the valve means |55 is provided which acts in response to increases in the 35 working pressure of the main pump P to raise the pressure of the control fluid and"hence of the fluid acting in the cylinder 51. Excess control and make-up fluid is supplied by the-makeup pump MP, and the excess fluid/.is returned 40 to the tank or reservoir through the valve means |55 and particularly the conduit 264. In order that this control valve means may be responsive to the working pressure, the ends of the bores |10 and |1| are connected to the passages 48 and 49, as previously described, so that the pressure of the working fluid may be transmitted to the valve means |55 for either direction of operationof the pump. The areas acted upon by the fluid supplied through ports |80 and |8| are equal so that the same force for a given working pressure is exerted regardless of the direction of operation of the pump. This force will, of course, vary directly with the working pressure in the pump and thus will serve to maintain in the conduit 250 a varying pressure increasing with increases in the working pressure of the main pump. This variation in pressure is, of course, transmitted to the cylinder 51 and thus will counteract and offset the increased reaction of the pistons on the wobbler and will thus maintain the pressure of the wobbler on the control member 5| constant and uniform. While this variation in pressure in the cylinder 51 maintains constant the pressure of the wobbler on the control member 5|, it nevertheless serves slightly to increase the displacement of the pump. This is accomplished by actual yielding of mechanical parts, the few thousandths of an inch necessary, as more fully explained in my copending application Serial No. 410,861, filed of even fluid for pre-loading the control member 5| is maintained at a constant pressure. The fluid for both make-up and pre-loading is supplied through conduit 253, which is connected to the port |88 of the pressure reducing valve means |56 and thus is always supplied with a fluid under 4constant pressure. Y

A different feed rate of operation of the motor may be obtained with shift of the valve 236 inwardly to a position where recess l238 bridges grooves 242 and 244. ,Under thoseV circumstances, control fluid is supplied through the conduit 214 to the end of the cylinder |1, causing the piston ||1 to take overcontrol of the crank |08 while the fluid in cylinder ||8 flows to tank through conduit 213, groove 243, groove 239, and the radial ports connecting the same to longitudinal passage 24|, and thence to the tank through 215. The screw ||9 for piston ||1 is adjusted to permit of increased shift of the control member 5| and hence increased displacement of the pump. This change in the position of the valve 236 does not affect the piston |22 and hence the motor continues to operate at a feed rate, but at one somewhat higher than the feed rate previously described.

The valve |92 might, of course, have been shifted to the left to the position shown in-Fig. 4 with the same results throughout except that control liuid would have been supplied to the conduit 269 and hence to the right hand end of cylinder 51, with the result that the direction of discharge of fluid from the pump P would have been reversed with respect to the direction of discharge described in connection with shift of the valve |92 to the right.

When the valve |92 is shifted to the traverse positions, shown m Figs.- 5 and 6, the wobblers of both the pump and the motor are adjusted to provide for maximum rate of operation of the motor and the feed valve means 235, and the pistons ||1 and ||8 controlled thereby are rendered inoperative. As clearly seen in Figs. 5 and 6, control fluid is still supplied to thecylinder 51 so as to cause the wobbler to be urged toward engagement with the control member 5|. With the valve shifted t the right, as shown in Fig. 5, fluid is supplied to the left hand end of the cylinder 51 through conduit 268, while the right hand end is connected to tank through the conduit 269 the same as described for the feed position of Fig. 3. When the valve is shifted to the left, as shown in Fig. 6, fluid is supplied tothe right hand end of the cylinder 51 through the conduit 269 to effect reverse operation of the pump.

Thoughfluid is thus continued to be supplied to the cylinder 51, the conduit 21| is in both 'traverse positions of the valve connected to tank. In Fig. this connection to tank is -through the recess 206 and longitudinal passage 205, while in Fig. 6 it is through recess 201 and longitudinal passage 205. With conduit 21| connected to tank, conduit 212 is likewise connected to tank and thus there is no fluid pressure in either the cylinder |1 or the cylinder I8, since in eitherposition of the valve 236 one cylinder will be connected directly to tank throughthe conduit 215, while the other cylinder will be connected to tank through the' conduit 212 and conduit 21|. The pistons ||1 andy ||8 thus will exercise no restraint on the crank |08, with the result that the pressure in the cylinder 51 will overcome the reaction of the pistons on the wobbler and the'pre-loading of the wobbler toshift the control member 5| to its extreme left position wherein the wobbler is positioned for maximum displacement ofthe pump.

Fluid is, however, supplied: to the right hand end of the cylinder |2| through conduit 210 which, in the position of the valve shown in Fig. 5, communicates with the longitudinal passage 200 through the recess 203 and, in the position of the valve shown in Fig. 6, communicates with the passage through the recess 204. Thus the piston |22 will be shifted to the left, as viewed in Fig 1, and the wobbler 94 will 'be adjusted to a minimum stroke position. This minimum stroke of the motor, coupled with the maximum displacement of the pump, will produce a traverse rate of operation of the motor for either direction of operation thereof.

Provision is made for the shift of the valve |92 hydraulically from one side of neutral through neutral to traverse posi-tion without having fluid pressure constantly acting on the ends of the valve |92. To that end, the plunger valves 2 I4 and 2|5 are provided-and are connected in a, unique circuit; If the valve is to be shifted from a position to the left of neutral to a traverse posi-- valve 2|5, such depression usually being effected automatically by dog means on a table or the like driven by the motor. As best seen in Fig. 5, when the valve 2 I8 of the valve means 2 |5 is depressed, control fluid in the conduit 25| is, through recess 222, supplied to the groove 226, thence by conduit 230 and recess 22| of the valve means 2|4 to conduit 266, discharging to the left hand end of the bore |9|. The right hand end of the bore |9| is connected by a conduit 261 to groove 221 of the valve means 2|5 and from thenceI through recess 22|, groove 228, conduits 23|, 232 and 233 to the chamber 2| 3, and thence to tank. Thus the control uid supplied to the left hand end of the bore |9| will shift the valve to its traverse position to the right of neutral, as shown in Fig. 5. When the valve 2 I8 of the valve means 2|5 is returned to its normal projecting position, conduit 25| is cut off from the conduit 230, disrupting the supply ,of control fluid to the conduit 266 and in turn connecting the conduit 230 to the conduit 261 which has been connected to tank, and thus interconnecting the ends of the bore I9 The fluid will be at no pressure but can flow backand forth from one end of the bore to the other, to permit manual shifting of the valve |92. Itis believed apparent that for a shift of the valve |92 from a position at the right of neutral to its traverse position at the left of neutral it is only necessary to depress the valve 2|8 of the valve means 2|4. Control fluid will then be supplied to the right hand end of the bore |9| 1through conduits 25| and 229, the latter of which is now bridged with the conduit 230 by the recess 222 of valve 2|4 so that the control fluid may then return to the valve means 2 5 where it flows through recess 22| to conduit 261 to the right hand end of the bore. The left hand end of the bore is connected to tank in the same manner as described for the right hand end in Fig. 5, but through the valve means 2 I4, I claim as my invention:

1. A pumping mechanism comprising, in combination a main pump, an auxiliary pump, for supplying make-up fluid to the main pump, and

means for controlling the pressure of the make` up fluid, said last mentioned means being responsive to the pressure of the fluid discharged by said main pump for governing the pressure of the fluid discharged by said auxiliary pump.

2. A pumping mechanism comprising in combination a variable displacement main pump, fluid operated displacement 'control means therefor, an auxiliary pump for supplying control fluid to said displacement control means, and valve means responsive to the pressure of the fluid discharged by said main pump governing the pressure of the fluid discharged by said auxiliary pump to said control means.

3. A pumping mechanism comprising, in combination, a main pump, control means therefor, an auxiliary pump, a discharge line leading from said auxiliary pump to the main pump control means, and by-pass valve means connected to said discharge line operable to maintain a predetermined pressure of the fluid in the discharge line and including means subjected to the pressure of said main pump urging said valve means to increase the pressure maintained in said discharge line.

4. A pumping mechanism/comprising, in combination, a main pump, hydraulically actuated means for controlling the output thereof, an auxiliary pump, a discharge line leading from said auxiliary pump to said hydraulically actuated means, a Aby-pass valve means connected to said discharge line and having an open and a closed position, the fluid in said discharge line acting on said valve means to open the same. and means connecting said main pump to said valve means whereby the 4main pump pressure urges said valve means toward closed position.

5'. In a hydraulic circuit, a main pump, an auxiliary pump, a discharge line leading from said `auxiliary pump, a by-pass valve means connected to said discharge line and having an open and a closed position, the fluid in said discharge line acting on said valve means to open the same, means acting on said valve means to maintain a constant pressure in said discharge line, and means for additionally subjecting said valve means to the discharge pressure of said main pump to increase the pressure maintained in said discharge line with an increase in the discharge pressure of said main pump.

6. In a hydraulic circuit, a reversible main pump having a pair of ports alternatively operable as discharge ports, an auxiliary pump, a discharge line leading from said auxiliary pump, a by-pass valve means connected to said discharge line and having an open and a cle-sed position, the fluid in said discharge line acting on said valve means to open the same, a plunger having two pressure surfaces of'equal area and operable when either ,surface is subject to pressure to ur-gesaid valve means to closed position, a conduit leading from one of the ports in said main pump to one of said pressure surfaces, and a second conduit leading Afrom the other port in said main pump to the remaining pressure surface.

7. In a hydraulic circuit, a variable displacement pump, means governing the displacement ef said pump, and means operable to increase the displacement of said pump with an increase in the working pressure of said pump.

increasing the pressure of the fluid supplied with an increase in the working pressure of said pump.

f sure of the fluid supplied by said auxiliary pump- 9. In a hydraulic circuit, a variable displacement pump having a wobbler, means governing the displacement of said pump including piston and cylinder means connected with the wobbler and operable when supplied with fluid under pressure to urge the wobbler toward increased displacement, an auxiliary pump for supplying control fluid to said piston and cylinder means, and by-pass valve means responsive to the working pressure of said flrst mentioned pump controlling the pressure of said auxiliary pump to increase the pressure of the control fluid with an increase in the working pressure of said flrst mentioned pump.

l0. In a hydraulic circuit, a variable displacement pump having a wobbler, means governing the displacement of said pump including piston and cylinder means connected with the wobbler and operable when supplied with fluid under pressure to urge the wobbler toward increased displacement, means placing a constant pre-load on the wobbler tending to restore the same to zero displacement, an auxiliary pump for supplying control fluid to said piston and cylinder means, and by-pass valve means responsive to the working pressure of said first mentioned pump controlling the pressure of said auxiliary pump to increase the pressure of the control fluid with an increase in the working pressure of said flrst mentioned pump.

11. In a hydraulic circuit, a variable displacement pump having a pivotally mounted wobbler, a control member engaging the wobbler to determine the tilt thereof, a flrst hydraulic device acting through said member to urge said wobbler to no-stroke position, a second hydraulic device connected with said wobbler and operable when supplied with fluid under pressure to urge said wobbler toward increased displacement of the pump, means for supplying fluid to said 4first hydraulic device at constant pressure to place a constant pre-load on the wobbler, and means for supplying fluid to said secondv hydraulic device at pressures increasing with increases in the working pressure of said flrst mentioned pump.

12. In a hydraulic circuit, a variable displacement pump having a pivotally mounted wobbler, a control member engaging the wobbler to determine the tilt thereof, a flrst hydraulic device acting through said member to urge said wobbler tol no-stroke position, a second hydraulic device connected with said wobbler and operable when supplied with fluid under pressure to urge said wobbler toward increased displacement of the pump, an auxiliary pump for supplying control fluid, by-pass valve means governing the presto said second hydraulic device, said by-pass valve means being subjected to the working pressure of the flrst mentioned pump andv increasing the pressure of the control fluid with increases in working pressure of the flrst mentioned pump, and a pressure reducing valve for maintaining constant the pressure of the control fluid supplied to said flrst hydraulic device.

13. In a hydraulic circuit, a variable displacement pump having a plurality of annularly arranged piston and cylinder devices, a drive shaft and a wobbler pivotally mounted on said shaft and engaging the pistons of said devices, the reaction of the pistons on said wobbler tending to return the same to no-stroke position, a control member determining the tilt of said wobbler, a

hydraulic device operable when supplied with said hydraulic device-including means for in' creasing the pressure of the control fluid with an increase in the working pressure of said pumpI the increase in force of said hydraulic device by the increase in control pressure beingv equal to the increased reaction of the pistons o'n said wobbler.

14. In a hydraulic circuit, a variable displacement pump having a plurality of annularly arranged piston and cylinder devices, a drive shaft and a wobbler pivotally mounted on said shaft and engaging the pistons of said devices, the reaction of the pistons o n said wobbler tending to return the same to no-stroke position, a control member determining' the tilt of said wobbler, a first hydraulic device acting through said control member to urge said wobbler to no-stroke position, a second hydraulic device operable when supplied with fluid under pressure to urge said wobbler toward a position of increased displacement of said pump, an auxiliary pump supplying control fluid to both hydraulic devices, a by-pass valve determining the pressure of the control fluid, a reducing valve determining the pressure of the control fluid supplied to said rst hydraulic device, the force of said second hydraulic device exceeding the sum of the forces of said first hydraulic device and the pistons, said by-pass valve means being subjected to the working pressure of said flrstmentioned pump and operating to increase the pressure of the control fluid with an increase in the working pressure of said pump, the increase in force of said hydraulic device by the increase in control pressure being equal to the increased reaction of the pistons on said wobbler.

15. In a hydraulic circuit, a variable displacement pump having a plurality of annularly arranged piston and cylinder devices, a drive shaft i A and a wobbler pivotally mounted on said shaft fluid, a reducing valve determining the pressin'e of the control fluid supplied to said first hydraulic device, the force of said second hydraulic device exceeding the sum of the forces of said first hydraulic deviceiand the pistons, said bypass valve means being subjected to the working pressure of said first mentioned pump and operating to increase the pressure of the control fluid with an increase in the Working pressure of said pump, the increase in force of said hydraulic device by the increase in control pressure being equal to the increased reaction of the pistons on said wobbler, and means for determining the position of said control member.

16. In a hydraulic circuit, a pump fordis charging operating fluid, hydraulically actuated means for reversing thedirection of discharge of said pump, means supplying control fluid and valve means governing the control fluid comprising a hydraulically shiftable valve and a plurality of plunger valves governing the control fluid normally to maintain said shiftablel valve under no pressure and to supply fluid under pressure for shifting the shiftable valve only when a plunger valve is actuated.

17. In a hydraulic circuit, a pump for discharging operating uid, hydraulically actuated means for reversing the direction of discharge of said pump, means supplying control fluid and valve means governing the control uid comprising a valve bore, a cylindrical valve slidable in the bore and having a neutral position and a shifted position on either side of neutral, and a pair of plunger valve means each having a normal position and a shifted position and each connected to control the supply of control fluid to one end of the valve bore and the exhaust of fluid from the opposite end of the valve bore,

' said plunger valve means in normal position interconnecting the ends of the valve bore.

18. In a hydraulic circuit, a pump for discharging operating fluid, hydraulically actuated means for reversing the direction of discharge of said pump, means supplying control fluid and valve means governing the control fluid comprising a valve bore, a cylindrical valve slidable in the bore and having a neutral position and a shifted position on either side of neutral, and a pair of governing valve meansV each connected to the supply of control fluid and additionally connected to one another, one of said governing valve means connected to one end of said valve bore and the other valve means connected to the opposite end of said valve bore, each of said valve means having a normal position interconnecting the ends of the valve bore when both governing valve means are 'n normal position, and each having a shifted position connecting one end of the valve bore to the supply of control fluid through the other valve means and the-opposite end of the valve bore to tank.

`GUNNAR. A. WAHLMARK. 

